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more fixed point work

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This commit is contained in:
Tomas Frydrych 2007-01-19 16:04:06 +00:00
parent f51d4659b8
commit f924e2bbf7
5 changed files with 136 additions and 68 deletions
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16
ChangeLog
View file

@ -1,3 +1,19 @@
2007-01-19 Tomas Frydrych <tf@openedhand.com>
* clutter/clutter-fixed.h.:
* clutter/clutter-fixed.c:
Added fast double to int and double to fixed point conversion
routines; changed CLUTTER_FLOAT_TO_FIXED to use it.
Replaced clutter_sqrti with fixed point implementation of the QIII
algorithm.
* clutter/clutter-behavior-path.c: use clutter_sqrti always
* clutter/clutter-alpha.c:
(sinc_func): replaced double -> int cast with CLUTTER_FLOAT_TO_INT
2007-01-18 Emmanuele Bassi <ebassi@openedhand.com>
* configure.ac: Post release bump to 0.3.0.

4
clutter/clutter-alpha.c
View file

@ -519,7 +519,6 @@ sincx1024_func (ClutterAlpha *alpha,
return CLUTTER_FIXED_INT (sine * CLUTTER_ALPHA_MAX_ALPHA);
}
#if 0
/*
* The following two functions are left in place for reference
@ -570,9 +569,10 @@ sinc_func (ClutterAlpha *alpha,
CLUTTER_NOTE (ALPHA, "sine: %2f\n", sine);
return (guint32) (sine * (gdouble) CLUTTER_ALPHA_MAX_ALPHA);
return CLUTTER_FLOAT_TO_INT ((sine * (gdouble) CLUTTER_ALPHA_MAX_ALPHA));
}
#endif
/**
* clutter_sine_func:
* @alpha: a #ClutterAlpha

6
clutter/clutter-behaviour-path.c
View file

@ -196,12 +196,12 @@ node_distance (const ClutterKnot *begin,
if (clutter_knot_equal (begin, end))
return 0;
#ifdef CFX_NO_FPU
#if 1
return clutter_sqrti ((end->x - begin->x) * (end->x - begin->x) +
(end->y - begin->y) * (end->y - begin->y));
#else
return (gint) sqrt ((end->x - begin->x) * (end->x - begin->x) +
(end->y - begin->y) * (end->y - begin->y));
return CLUTTER_FLOAT_TO_INT(sqrt((end->x - begin->x) * (end->x - begin->x) +
(end->y - begin->y) * (end->y - begin->y)));
#endif
}

163
clutter/clutter-fixed.c
View file

@ -353,14 +353,6 @@ clutter_sqrtx (ClutterFixed x)
* on ARM this function is about 5 times faster than c-lib sqrt, whilst
* producing errors < 1%.
*
* (There are faster algorithm's available; the Carmack 'magic'
* algorithm, http://www.codemaestro.com/reviews/review00000105.html,
* is about five times faster than this one when implemented
* as fixed point, but it's error is much greater and grows with the
* size of the argument (reaches about 10% around x == 800).
*
* Note: on systems with FPU, the clib sqrt can be noticeably faster
* than this function.
*/
int t = 0;
int sh = 0;
@ -448,68 +440,121 @@ clutter_sqrtx (ClutterFixed x)
* clutter_sqrti:
* @x: integer value
*
* A fixed point implementation of square root for integers
* Very fast fixed point implementation of square root for integers.
*
* This function is about 10x faster than clib sqrt() on x86, and (this is
* not a typo!) more than 800x faster on ARM without FPU. It's error is < 5%
* for arguments < 132 and < 10% for arguments < 5591.
*
* Return value: integer square root (truncated).
* Return value: integer square root.
*
*
* Since: 0.2
*/
gint
clutter_sqrti (gint x)
clutter_sqrti (gint number)
{
int t = 0;
int sh = 0;
unsigned int mask = 0x40000000;
/* This is a fixed point implementation of the Quake III sqrt algorithm,
* described, for example, at
* http://www.codemaestro.com/reviews/review00000105.html
*
* While the original QIII is extremely fast, the use of floating division
* and multiplication makes it perform very on arm processors without FPU.
*
* The key to successfully replacing the floating point operations with
* fixed point is in the choice of the fixed point format. The QIII
* algorithm does not calculate the square root, but its reciprocal ('y'
* below), which is only at the end turned to the inverse value. In order
* for the algorithm to produce satisfactory results, the reciprocal value
* must be represented with sufficient precission; the 16.16 we use
* elsewhere in clutter is not good enough, and 10.22 is used instead.
*/
ClutterFixed x;
unsigned long y, y1; /* 10.22 fixed point */
unsigned long f = 0x600000; /* '1.5' as 10.22 fixed */
float flt = number;
float flt2;
if (x <= 0)
return 0;
x = CLUTTER_INT_TO_FIXED (number) / 2;
if (x > (sizeof (sqrt_tbl)/sizeof(ClutterFixed) - 1))
{
/*
* Find the highest bit set
*/
#if __arm__
/* This actually requires at least arm v5, but gcc does not seem
* to set the architecture defines correctly, and it is probably
* very unlikely that anyone will want to use clutter on anything
* less than v5.
*/
int bit;
__asm__ ("clz %0, %1\n"
"rsb %0, %0, #31\n"
:"=r"(bit)
:"r" (x));
/* The QIII initial estimate */
y = * ( unsigned long * ) &flt;
y = 0x5f3759df - ( y >> 1 );
flt = * ( float * ) &y;
/* make even (2n) */
bit &= 0xfffffffe;
#else
/* TODO -- add i386 branch using bshr */
int bit = 30;
while (bit >= 0)
{
if (x & mask)
break;
/* Now, we convert the float to 10.22 fixed. We exploit the mechanism
* described at http://www.d6.com/users/checker/pdfs/gdmfp.pdf.
*
* We want 22 bit fraction; a single precission float uses 23 bit
* mantisa, so we only need to add 2^(23-22) (no need for the 1.5
* multiplier as we are only dealing with positive numbers).
*
* Note: we have to use two separate variables here -- for some reason,
* if we try to use just the flt variable, gcc on ARM optimises the whole
* addition out, and it all goes pear shape, since without it, the bits
* in the float will not be correctly aligned.
*/
flt2 = flt + 2.0;
y = * ( long * ) &flt2;
y &= 0x7FFFFF;
mask = (mask >> 1 | mask >> 2);
bit -= 2;
}
#endif
sh = ((bit - 6) >> 1);
t = (x >> (bit - 6));
}
else
{
return (sqrt_tbl[x] >> CFX_Q);
}
/* Now we correct the estimate, only single iterration is needed */
y1 = (y >> 11) * (y >> 11);
y1 = (y1 >> 8) * (x >> 8);
x = sqrt_tbl[t];
y1 = f - y1;
y = (y >> 11) * (y1 >> 11);
if (sh > 0)
x = x << sh;
else if (sh < 0)
x = (x >> (1 + ~sh));
return (x >> CFX_Q);
/* Invert, round and convert from 10.22 to an integer
* 0x1e3c68 is a magical rounding constant that produces slightly
* better results than 0x200000.
*/
return (number * y + 0x1e3c68) >> 22;
}
/* <private> */
const double _magic = 68719476736.0*1.5;
/* Where in the 64 bits of double is the mantisa */
#ifdef LITTLE_ENDIAN
#define _CFX_MAN 0
#else
#define _CFX_MAN 1
#endif
/*
* clutter_double_to_fixed :
* @value: value to be converted
*
* A fast conversion from double precision floating to fixed point
*
* Return value: Fixed point representation of the value
*
* Since: 0.2
*/
ClutterFixed
_clutter_double_to_fixed (double val)
{
val = val + _magic;
return ((gint32*)&val)[_CFX_MAN];
}
/*
* clutter_double_to_int :
* @value: value to be converted
*
* A fast conversion from doulbe precision floatint point to int;
* used this instead of casting double/float to int.
*
* Return value: Integer part of the double
*
* Since: 0.2
*/
ClutterFixed
_clutter_double_to_int (double val)
{
val = val + _magic;
return ((gint32*)&val)[_CFX_MAN] >> 16;
}
#undef _CFX_MAN

15
clutter/clutter-fixed.h
View file

@ -118,10 +118,9 @@ typedef gint32 ClutterAngle; /* angle such that 1024 == 2*PI */
#define CLUTTER_FIXED_TO_FLOAT(x) ((float) ((int)(x) / 65536.0))
#define CLUTTER_FIXED_TO_DOUBLE(x) ((double) ((int)(x) / 65536.0))
#define CLUTTER_FLOAT_TO_FIXED(x) \
( (ABS(x) > 32767.0) ? (((x) / (x)) * 0x7fffffff) \
: ((long)((x) * 65536.0 + ((x) < 0 ? -0.5 \
: 0.5))) )
#define CLUTTER_FLOAT_TO_FIXED(x) _clutter_double_to_fixed((x))
#define CLUTTER_FLOAT_TO_INT(x) _clutter_double_to_int((x))
#define CLUTTER_INT_TO_FIXED(x) ((x) << CFX_Q)
#define CLUTTER_FIXED_INT(x) ((x) >> CFX_Q)
@ -180,6 +179,14 @@ ClutterFixed clutter_sini (ClutterAngle angle);
ClutterFixed clutter_sqrtx (ClutterFixed x);
gint clutter_sqrti (gint x);
/* <private> */
extern inline
ClutterFixed _clutter_double_to_fixed (double value);
extern inline
ClutterFixed _clutter_double_to_int (double value);
G_END_DECLS
#endif